Various devices have long been available for opening clams and oysters. In most cases a given device is suitable for opening either of the shellfish, which is true of the present invention as well, and hence when clams are referred to herein it is to be understood that oysters and other bivalves are to be included.
One category of prior art openers utilizes an opening arm hinged to a fixed base, from the simple device of U.S. Pat. No. 1,597,622 to the more involved designs of U.S. Pat. Nos. 837,465, 1,212,464 and 4,255,835. The latter all include some form of pawl and ratchet to advance the opener knife or point incrementally into the clam in a linear, not angular, fashion by complicated mechanisms unsuitable for handheld plier-type devices.
The other catetory of prior art openers consists of simpler plier-type tools squeezed by hand to close jaws about a clam and wedge its half shells apart. The opener of the invention is generally in that category though as will be seen it could be adapted to a fixed base. U.S. Pat. Nos. 2,473,608 and 3,706,114 disclose scissors-style openers having one or more fixed pivot points. The opener of U.S. Pat. No. 3,685,097 incorporates an adjustable pivot point to accomodate clams of different sizes and to achieve variable mechanical advantage. In none of these plier-type prior art openers is a pawl and ratchet employed to close the jaws incrementally about the clam.
The present invention applies the pawl and ratchet principle to a hand-squeezed plier-type opening tool to permit clams of various sizes to be opened by successive squeezings with maximal mechanical advantage and therefore requiring minimal physical effort. In addition, and of equal importance, is the matter of safety. Since the tool of the invention closes in increments it is impossible accidentally to slip off the clam and injure the fingers of the operator.